I have a home in Colorado that was built in 1959. It has 2 plug outlets and I replaced them with grounding 3 plug outlets. I was told that since the electical wiring was in conduit that I did not have to run an additional ground wire to each outlet. I've also been told that each outlet should be grounded by attaching a ground wire to the receptacle and the outlet box.

I've tested each outlet and none of them show an open ground.

Is it necessary to ground each outlet by attaching a ground wire to the outlet box?

Yes it is required that you attach a green or bare wire from the box using a ground screw to the grounded outlet. The whole assembly can be found in your home center and is easy to install. This would make it code compliant if your home wired as you say in conduit.

the previous post confuses me since we also have metal boxes and where the conduit is bonded to the box we were told since we didnt use metal switch covers and outlet covers if we removed one of the insulator gaskets and used switches and outlets that were self grounding we were not required to use grounding wires to the back of the box since the mounting outlet or switch made contact to the box. does it make a difference if the outlet is wired with tails or if it is feeded through or do we have to rewire every switch and outlet now? the inspector didnt have a problem with it except where one cover was metal we had to swap that out.

the previous post confuses me since we also have metal boxes and where the conduit is bonded to the box we were told since we didnt use metal switch covers and outlet covers if we removed one of the insulator gaskets and used switches and outlets that were self grounding we were not required to use grounding wires to the back of the box since the mounting outlet or switch made contact to the box. does it make a difference if the outlet is wired with tails or if it is feeded through or do we have to rewire every switch and outlet now? the inspector didnt have a problem with it except where one cover was metal we had to swap that out.

In general you always should ground a receptacle as I describe above. However there are exceptions one being a self grounding outlet that is clearly marked self grounding(not all outlets are). I was talking in general as the most outlets are not self grounding. Although you have been approved by the inspector to use plastic covers the screws still are metal and connect to the yoke to me that isn't the completely insulated. But that is my opinion and inspectors are the one taking that responsibility for the instalation. I would look at 250.146 of the NEC to see if you comply on your instalation.

3-story 12unit condo: conduit
block home 1-1/2 story over basement: conduit
NYC home conduit and metal boxes same for all friends and neighbors.
VA new row house with finished walk-out to grade basement conduit
Bostom brick home with finished attic was rehabbed and rewired by prior owner from knob and tube to all new wiring: all conduit and metal boxes

3-story 12unit condo: conduit
block home 1-1/2 story over basement: conduit
NYC home conduit and metal boxes same for all friends and neighbors.
VA new row house with finished walk-out to grade basement conduit
Bostom brick home with finished attic was rehabbed and rewired by prior owner from knob and tube to all new wiring: all conduit and metal boxes

strange.

It's not all that strange.
Like Ravens was mentioning it's not common for homes to be using conduit throughout the home. The exception that I've heard about is the Chicago area.